Early ultrastructural changes in rat duodenal mucosa associated with cysteamine-induced ulcer.

The early morphologic sequelae induced by the duodenal ulcerogen, cysteamine, have been studied in rats by transmission electron microscopy. Cysteamine was administered per os at 70 mg/100 g body wt to groups of female rats sacrificed at 30 min, 1, 2, 4, 8, 12, 20, and 24 hr after chemical treatment, and duodenal tissue sampled from the antimesenteric side of the proximal duodenum, where ulcers develop, was studied. Emphasis was placed on early times as our previous scanning electron microscopic data had demonstrated enhanced in situ cellular necrosis and surface cavitation at 2-4 hr after cysteamine treatment. Results indicated intracellular changes as early as 30 min after treatment and prior to damage of the columnar cell microvilli or epithelial tight junctions. A staging of observed cellular degenerative changes suggested early apical endoplasmic reticular swelling and loss of cytoplasmic ground substance, followed later by moderate internal disruption of mitochondria. Through these stages the cell surface microvilli remained morphologically normal. Subsequently, microvilli degenerated and mitochondrial fine structure became severely disrupted and cell contents were expelled. Deeper villous changes such as separation of columnar cells from the lamina propria and alterations of selected elements within the lamina propria were observed. These data suggest that intracellular cytotoxic reactions at the villous tips occur early and may precede the influence of intraluminal damaging factors induced by cysteamine.